The present invention relates to a degasser snorkel used to circulate molten metal from a ladle to a vacuum vessel and, in particular, to an interlocking snorkel refractory of the degasser snorkel.
The problem which the invention seeks to overcome relates to the field of degasser snorkels used to circulate metal, e.g., steel, from a ladle to a vacuum vessel. In such apparatuses, the degasser snorkel is attached in open communication with the base of the vacuum vessel and is positioned over a ladle of molten metal so as to be immersed in the molten metal. Upon drawing a vacuum in the vacuum vessel, the molten metal rushes up through the degasser snorkel into the vacuum vessel releasing entrapped gasses. Removal of the entrapped gasses improves the properties of the metals since these gasses can cause brittleness in the metal.
The inner surface of the snorkel is normally lined with a refractory lining in the form of refractory bricks. The refractory lining is subject to various modes of failure which can affect the life of the snorkel. The first mode is the physical integrity of the refractory lining which can be affected by thermal movement thereof during passage of the molten steel through the snorkel. If the movement or shifting of the refractory lining is severe enough, the refractory bricks may fall out of the snorkel. A second mode of failure is "channeling" which involves the molten steel following the joints between the refractory bricks and thereby forming a wear pattern. The above-mentioned forms of failure each contribute to a shortened life of the degasser vessel and thereby force the removal of the vessel from service for repairs.
Further, in conventional degasser snorkels, a plurality of bolts are disposed around the bottom of the inner refractory lining in order to aid in vertically supporting the refractory bricks on the surrounding casing. However, such bolts tend to burn off after continued use of the snorkel and, hence, further contribute to a shortened life thereof.
U.S. Pat. No. 3,422,857 (Napora) relates to a degasser device and, in particular, a snorkel 10. Napora discloses that the bricks forming the outer cylinder may contain on all surfaces in contact with adjacent brick, complementary tongues and grooves for interlocking with the adjacent shapes. However, the bricks having the interlocking means are part of an outer refractory surface rather than an inner refractory surface and also the interlocking means is comprised by a tongue and groove type connection and not the particular interlocking means of the present invention.
U.K. Patent Application No. 2,145,740 relates to an immersion tube or snorkel for vacuum-refining molten steel. In particular, the U.K. '740 device provides an immersion tube for vacuum-refining molten steel, which when vacuum-refining molten steel by the RH-type vacuum-refining process, is capable of withstanding use for multiple cycles of such refining. The U.K. '740 device further teaches that the distribution of thermal stress produced by a sudden thermal variation in each of the plurality of magnesia-chrome bricks forming the inner bore of the immersion tube, becomes more uniform as the shape of the rectangular face of each brick which forms the inner bore is formed closer to a square in shape. However, the U.K. '740 device does not disclose the particular brick configuration to allow interlocking of the bricks as in the present invention.
British Patent No. 1.270.660 (Hale) relates to a construction of a metallurgical furnace hearth or floor and, in particular, to the construction of carbon lining members for such floors. As best seen in FIGS. 1 and 2, the hearth has two layers of carbon lining members in the form of large rectangular beams 10. The beams are surrounded by a jacket or casing 9. The beams 10 include corrugations which extend longitudinally along opposite longitudinal sides thereof and which are formed by ridges 18 having corresponding grooves between them. Therefore, Hale does not relate to the inner refractory lining of the degasser snorkel, but rather to a furnace floor having corrugated beams.
The German Patent NO. 1,111,224 relates to a device for the vacuum treatment of liquid metals including a vacuum vessel and a pair of refractory-lined tubes 1 and 2, wherein one of the tubes acts as a gas lift. An outer steel tube 3 surrounds the pair of refractory-lined tubes 1 and 2. The Tubes 1 and 2 may be formed of several pieces fitted together at joints 10 (see FIG. 2). The respective joints 10 of the tube 1 and tube 2 may be staggered as shown in FIG. 3. While the German '224 device teaches a refractory lining formed of a plurality of sections joined together, the sections are tubular in shape rather than being formed of a plurality of interlocking bricks as in the present invention.
U.S. Pat. No. 4,055,336 (Massin) relates to a container for molten metal having a floor and side walls and having an inner wall lining made up of a plurality of slabs 5 and 7 of refractory heat insulating material, wherein at least some of the slabs have opposite edges castellated so as to include a plurality of teeth with slots defined therebetween to form joints 6. However. Massin does not relate to a degasser snorkel, nor does he disclose utilizing the joints 6 to interlock refractory bricks forming the refractory inner lining of a degasser snorkel.
U.S. Pat. No. 3,607,228 (Todd). U.S. Pat. No. 3,056,595 (Knuppel et al.). U.S. Pat. No. 3,203,687 (Wynne et al.). U.S. Pat. No. 3,203,688 (Sieckman et al.). U.S. Pat. No. 4,595,178 (Kato et al.). U.S. Pat. No. 3.326.543 (Kienow) and U.S. Pat. No. 3,521,873 (Matsuda) all teach various degassing apparatuses including snorkels for handling molten metal. The snorkels of the various teachings include a refractory inner lining formed of either a one piece member or by a plurality of refractory bricks. However, none of these references discloses refractory bricks which interlock with one another as in the present inVention.
Finally. U.S. Pat. No. 4,441,298 (Limousin) relates to nesting modular elements which may be used in building construction for enclosure walls and the like. As best seen in FIGS. 1 and 2, the modular elements may include an upper portion having projections 13 formed thereon and a lower portion having a large recess 15 formed therein. While Limousin teaches modular elements that can be engaged with one another to form, for example, a wall, his invention has nothing to do with a degasser snorkel for the handling of molten metal. Clearly, the extreme thermal expansion peculiar to a degasser snorkel was not contemplated by Limousin.